Improvement in the manufacture of white lead



UNITED STATES PATENT OFFICE.

THOMAS OOBLEY, OF LONDON, ENGLAND.

Specification forming part of Letters Patent No. 38,283, dated April 28, 1863.

['0 all whom it may concern.-

Be it known that I, 'Iuorms OoBLEY, of the city of London, Great Britain, have invented certain Improvements in the Manufacture of White Lead, (meaniu g carbonates of lead 5 and I do hereby declare that the following is a description of my invention sutiicient to enable those skilled in the art to practice it-that is to say:

Having first ground or crushed the ore to be acted upon, I then put it upon a simply-constructed furnace consisting of a surface of tireclay tiles, iron plates, or otherwise, and carefully roast it, regulating the heat as much as possible, so as not to form insoluble compounds by the vitrification or other reducing in fluences. It I am about to form pigment white lead, meaning pure white lead, I treat the roasted ore, in the first instance to form the standard lye, with the acetic acid of commerce, (where theore is very impure with a solution of the neutral acctate,) either in a gaseous or liquid form, the latter obtainable either by decomposition of alkaline acetates or acetatesformed from the earthy bases ofvaporized acetic acid, in which case the vapor or gas is introduced by means of a pipe from an apparatus for that purpose into a closed tank or vessel, which is divided into two parts by means of a finely-perforated diaphragm, upon which the roasted ore is placed, and which is kept wet in ordertocondense the vapor. Thequantity of acid which I employ in the process depends entirely upon the percentage of lead in tions as to form a subacetate of lead-that is tosay, the acid supersaturated withlead. The liquor obtained in this manner is brightened by passing it through animal charcoal or other decoloriziu g matter, and then precipitated with carbonic acid. I propose to obtain my carbonic acid by decomposing carbonaceous matters or from by-products given ofi' in the manufacture of silicate of soda, from carbonate of baryta or carbonate of soda, or of chloride of barium, or by the decomposition of marble, limestone, dolomite, magnesite, or any other of the alkaline carbonates, either obtained by the direct application of the said carbon ates, or by double decomposition, or from the carbonates or protocarbonates of iron or other available metallic carbonate;

When I use carbonic acid I always prefer to apply it in a heated state, and,furthermore, to purify it before use by passing it through a solution of copper or lead, or by any other well-known means. The method I adopt for bringing the carbonic acid into combination with the liquid, so as to cause precipitatiom'is,

as follows:- The liquor is allowed to percolate through a large holder, and meets the gas, which is introduced at the bottom of the said holder by means of a series of pipes. The excess of oxide in the subacetate is thus thrown down as carbonate of lead, which is allowed to settle. The liquor is then drawn 0d", and the precipitate washed. Then to render it into an oxiearbonate, or partiallyso, in which form it corresponds with the lead made by the corrosive process, I make use of a caustic alkaline lye possessing great affinity for carbonic acidas baryt-a or lime or any other alkaline earth-to withdraw a certain amount of earbonic acid, which is preferably efl'ected by boiling it in the same lye. After being dried in the ordinary manner it is then ready for market. I now treat the neutral liquor with a fresh supply of ore prepared as before until a subacetate is again formed, and again I precipitate as before, and continue charging and precipitating alternately. Hence the cost of the acetic acid becomes nominal, as I only use it asacarrier.

In producing white lead, which is used by potters, porcelain manufacturers, color-makers, and others, I employ a cheaper course of obtaining acetic acid-that is to say, I use the crude pyroligneous acid of commerce as a liquid, or the vapor of the said acid, or pyroligneous gas produced from dry distillation of wood, or a solution of the brown neutral. acetate. In this process I take the pyroligneous liquor and mix the ore with it, taking the latter warm from the calcining-furnace, using the necessary proportions of each. I then allow it to.stand, lixiviate itwith hot water, brighten it as before described, then precipitate it in the manner before mentioned. If the vapor from the acid itself is used, then it must be applied to the wet calcined ore through perforations in the manner described in the former process. When pyroligneous gases are used the calcined ore in a wet state must be placed in an apparatus supplying the place of the condenser in the ordinary process of distilling wood.

The liquor obtained by any of the last-de- 'potters or glazing lead greater flexibility, I

introduce a solution of borax into the lead by grinding or other available means, either produced from an alkaline boraie or otherwise from boracic acid. The strength of the solution will depend upon the nature of the pigments to be treated. For practical purposes I prefer the refined borax of commerce, and to introduce it at the last stage of washing.

I am aware that it is not new to make carbonate of lead by precipitation from the basic acetates. Neitherisitnew to make clichy-white by precipitation from a basic salt of lead by means of carbonic acid, nor to precipitate from solutions of native ores a leaden sponge, processes all of which are well known, and may be found describedin Mnspratts Chemistry. My process difl'ers from these, inasmuch as I do not use the metal or basic acetates or litharge to precipitate from. Neither do I employ the ore to produce a metallic sponge; but, having first pulverized or crushed the ore, I obtain directly therefrom a pure white lead by the process as above described. The advantages of this method of mauufacture are numerous and important. Isave the cost of making metallic lead or litharge from the ores and the time required to oxidize the former. I can use ore carbonates which are too poor to smelt. In smelting poor carbonates there is a very great loss of metal; but by using them in my process all the lead is saved, being taken up direct in white lead, and Iain enabled not only to save time, but to use ores otherwise of no value or too poor for smelting,

producing at low cost of manufacture a very fine and high-colored white lead.

Having now described the natureof my invention and how the same is carried into operation and the results obtained, I wish it understood that what I claim is I 1. The manufacture of white lead from crushed or ground native ore carbonates of lead by the process set forth, or by means substantially the same.

2. The method of treating precipitated white lead with acaustic alkaline solution for the purpose of producing an oxicarbonate of lead, by which it is rendered more amorphous and less crystalline and the covering properties of the lead are largely increased.

TH. OOBLEY.

Witnesses:

"SAML. ARGHBUTT,

THOS. Fox,

12 Oopthall Court, London. 

